Conventionally, a time-interleaved A/D converter is made up of four unitary A/D conversion units, a maximum value of amplitude and a DC offset value of a conversion output of each unitary A/D conversion unit are calculated through a digital operation, and in order to make the resultant calculated values equal to the maximum amplitude value and the DC offset value of the output of a first unitary A/D conversion unit, conversion gains and DC offset values of the remaining three unitary A/D conversion units are corrected by using an LMS (Least Mean Square) algorithm (for example, refer to Non-Patent Document 1).
Also, conventionally, in a time-interleaved A/D converter which performs calibration by using a reference A/D converter, each unitary A/D conversion unit is synchronized with the reference A/D converter to obtain a reference signal for each sample (for example, refer to Patent Document 1).    Non-Patent Document 1: C Hsu (C. Hsu et al., “An 11b 800 MS/s time-interleaved ADC with digital background calibration”, 2007 IEEE International Solid State Circuits Conference (ISSCC), Session 25.7, pp. 464-465 (2007))    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2007-150640